Kefayati Sarah, Milner Jaques S, Holdsworth David W, Poepping Tamie L
Department of Physics and Astronomy, University of Western Ontario, London, ON, Canada.
Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada.
PLoS One. 2014 Jul 9;9(7):e98209. doi: 10.1371/journal.pone.0098209. eCollection 2014.
Atherosclerotic disease, and the subsequent complications of thrombosis and plaque rupture, has been associated with local shear stress. In the diseased carotid artery, local variations in shear stress are induced by various geometrical features of the stenotic plaque. Greater stenosis severity, plaque eccentricity (symmetry) and plaque ulceration have been associated with increased risk of cerebrovascular events based on clinical trial studies. Using particle image velocimetry, the levels and patterns of shear stress (derived from both laminar and turbulent phases) were studied for a family of eight matched-geometry models incorporating independently varied plaque features - i.e. stenosis severity up to 70%, one of two forms of plaque eccentricity, and the presence of plaque ulceration). The level of laminar (ensemble-averaged) shear stress increased with increasing stenosis severity resulting in 2-16 Pa for free shear stress (FSS) and approximately double (4-36 Pa) for wall shear stress (WSS). Independent of stenosis severity, marked differences were found in the distribution and extent of shear stress between the concentric and eccentric plaque formations. The maximum WSS, found at the apex of the stenosis, decayed significantly steeper along the outer wall of an eccentric model compared to the concentric counterpart, with a 70% eccentric stenosis having 249% steeper decay coinciding with the large outer-wall recirculation zone. The presence of ulceration (in a 50% eccentric plaque) resulted in both elevated FSS and WSS levels that were sustained longer (∼20 ms) through the systolic phase compared to the non-ulcerated counterpart model, among other notable differences. Reynolds (turbulent) shear stress, elevated around the point of distal jet detachment, became prominent during the systolic deceleration phase and was widely distributed over the large recirculation zone in the eccentric stenoses.
动脉粥样硬化疾病以及随后的血栓形成和斑块破裂并发症与局部剪切应力有关。在病变的颈动脉中，狭窄斑块的各种几何特征会引起剪切应力的局部变化。基于临床试验研究，更高的狭窄严重程度、斑块偏心度（对称性）和斑块溃疡与脑血管事件风险增加有关。使用粒子图像测速技术，对一组八个匹配几何模型的剪切应力水平和模式（包括层流和湍流阶段）进行了研究，这些模型独立改变了斑块特征，即狭窄严重程度高达70%、两种斑块偏心形式之一以及斑块溃疡的存在情况。层流（总体平均）剪切应力水平随着狭窄严重程度的增加而升高，自由剪切应力（FSS）为2 - 16 Pa，壁面剪切应力（WSS）约为其两倍（4 - 36 Pa）。与狭窄严重程度无关，在同心和偏心斑块形成之间的剪切应力分布和范围存在显著差异。在狭窄顶端发现的最大WSS，与同心模型相比，在偏心模型的外壁上沿外壁的衰减明显更陡，70%偏心狭窄的衰减陡度高出249%，与大的外壁回流区一致。溃疡的存在（在50%偏心斑块中）导致FSS和WSS水平升高，与未溃疡的对应模型相比，在收缩期持续时间更长（约20毫秒），还有其他显著差异。雷诺（湍流）剪切应力在远端射流分离点周围升高，在收缩期减速阶段变得突出，并广泛分布在偏心狭窄的大回流区内。
